Advantageous metal-atom-escape towards super-hydrophilic interfaces assembly for efficient overall water splitting

Controllably constructing the functional microscopic surfaces, especially via the escape of metal atoms from extremely stable texture to achieve super-hydrophilic interfaces, as efficient bifunctional catalysts for water splitting is a daunting challenge but critical for sustainable economic development. Based on hydrothermal coordination strategy, we take advantage of strong oxidizing property of nitrate ions to realize temperaturecontrollable atom-escape of metal Ni for self-assembling super-hydrophilic hydroxide FeNi-OH on nickel base as electrocatalysts of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Such distinctive Ni source, resulting in improved ohmic contact and mechanical robustness of catalysts, in conjunction with super-hydrophilicity-accelerated bubble separation and electrolyte contact, endows the catalyst with excellent electrocatalytical activity for both HER and OER in alkaline solution. Super-hydrophilic FeNi-OH delivers the current density of 50 mA cm-2 at overpotentials of 236 mV for OER and 196 mV for HER. Water electrolysis with FeNi-OH as anode and cathode demands a cell voltage of 1.664 V to drive 50 mA cm-2 in 1.0 M KOH, continuously operating for 25 h. This study opens up an avenue in establishing super-hydrophilic structure via self-assembly of the escaped atoms, broadening the horizon on low-cost iron-containing catalyst preparation for energy conversions.

Automated summary

This study successfully achieved the temperature-controllable atom-escape of metal Ni using the strong oxidizing property of nitrate ions, resulting in self-assembling super-hydrophilic hydroxide FeNi-OH on nickel base for efficient bifunctional catalysis in water splitting. The super-hydrophilic FeNi-OH showed excellent electrocatalytical activity for both HER and OER reactions in alkaline solution, providing a promising avenue for low-cost iron-containing catalyst preparation for energy conversions.